Inflammation occurs when tissues are damaged. Inflammation can often be characterized by redness, swelling, heat, and pain. Cells involved in the inflammatory response include polymorphonuclear luekocytes (PMN), macrophages, and mast cells. One type of inflammatory response is an allergic response, or Type I hypersensitivity response. Upon exposure to an allergen, B cells produce immunoglobulin E (IgE), which complexes with mast cells, resulting in the release of toxic cytokines and inflammatory mediators such as histamine, protease, prostaglandin, and leukotriene. In atopic individuals, this IgE-mast cell complex persists longer, resulting in an over-production of mediators and in inflammation, with the key mediator of inflammation being histamine.
In felines, as in other animals, inappropriate or excess inflammatory response can cause significant health problems. For example, a number of disorders present on a regular basis for veterinary treatment, including inflammatory bowel disease, arthritis, and dermatitis. Some conditions may be treated with medication, but such medications may be expensive and they can often be accompanied by undesirable side effects. It would be preferable to provide relief from such conditions by means of components in the feline diet.
Lipids are recognized as important constituents of mammalian diets, and certain lipids have been demonstrated to have a direct impact on specific metabolic processes. One such group of lipids are the polyunsaturated fatty acids (PUFA's), which can generally be classified as omega-3 (n-3) or omega-6 (n-6) fatty acids. The essential fatty acid arachidonic acid, for example, is required for steroid synthesis and is recognized as having a role in both the immune response and the in cardiovascular disease. Both the n-6 and n-3 series of fatty acids have been shown to influence the inflammatory response through the eicosanoid pathway. Eicosanoids are metabolites of arachidonic acid or eicosapentaenoic acid which are released from cellular membranes in response to cell injury. Arachidonic acid is used in the production of certain prostaglandins, leukotrienes and thromboxanes that promote an inflammatory response. Eicosapentaenoic acid (EPA) is used in the production of certain prostaglandins, leukotrienes and thromboxanes that have been demonstrated to reduce the inflammatory response.
The ability of diet to influence eicosanoid production, thereby influencing the production of mediators of the inflammatory response, has been demonstrated in the dog. Studies have shown that altering the dietary omega-6 to omega-3 fatty acid ratio from 100:1 to 5:1 decreases skin production of LTB4 and increases skin production of LTB5, thus decreasing the inflammatory potential in those dogs.
In the dog, certain fatty acids can be derived from shorter chain fatty acids present in the diet. Dietary linoleic acid, for example, can be absorbed and elongated to form arachidonic acid with the help of specific canine elongase and desaturase enzymes. Alpha-linolenic acid (ALNA) can be elongated to form EPA using similar enzymes. In humans, ALNA can be desaturated and elongated to EPA and DHA. Cats, however, cannot utilize dietary C 18 essential fatty acids such as ALNA due to a lack of the necessary enzyme. It has been generally accepted, therefore, that cats require 20-carbon long chain essential fatty acids such as arachidonic acid. Feline requirements for essential fatty acids in the diet cats have generally not been determined, and little is known about the effects of dietary n-3 fatty acids on the feline immune system.
Accordingly, there is still a need in the art for a dietary composition for felines which provides sufficient levels of essential fatty acids to reduce inflammatory response.